When can an independent candidate file for nomination?
It is generally required that the petition for nomination be filed after the primary election
Primaries and caucuses serve to instruct party delegates to their respective national conventions which candidate(s) to support the nomination of for various political offices. For instance, before the official nomination and acceptances thereto for the office of President of the United States, the Party not in control of the Presidency entertains a field of candidates, all of whom describe themselves as "running for President". In reality, however, each is in pursuit of the nomination as…
In 2008, he first had to get the Democratic nomination, so his opponent was Hillary Clinton. Once he got the nomination, his opponent was Republican party candidate John McCain, and Mr. Obama defeated him. In 2012, the president's opponent was Republican candidate Mitt Romney, and Mr. Obama defeated him to win re-election.